The present invention relates generally to container sealing apparatus and/or to a method for sealing a container. Embodiments of the present invention are concerned particularly with the use of induction heating to apply sealing material to an open top of a container to seal the container.
Induction sealing machines can be used to apply sealing material to the open tops of a variety of containers to seal the containers. In one currently available machine, a ceramic cutting punch is used both to cut a portion of sealing material from a web and to transfer the cut portion of sealing material to the container in a single stroke. The cut portion of sealing material is then inductively heated whilst held against the open top of the container by the cutting member.
The use of ceramic material is advantageous since it is extremely hardwearing. Moreover, when the electrical induction coil is activated to heat the cut portion of sealing material, the cutting punch is not itself inductively heated provided that the ceramic material is electrically insulating. This ensures that there is no thermal expansion of the cutting punch and that the induction energy is not wasted by being drawn into the cutting punch.
Ceramic materials are not, however, suitable for use in situations where the sealing geometry is complex since it becomes economically unfeasible to manufacture a ceramic cutting punch with the required geometry. The use of a ceramic cutting punch can also be problematic when sealing glass containers since any misalignment between the cutting punch and container could cause the container to shatter when the cutting punch presses the cut portion of sealing material onto the rim of the container. It would, therefore, be desirable to provide an apparatus and method for sealing a container which can be used in situations for which the induction sealing machine outlined above, employing a ceramic cutting punch, and similar machines are not ideally suited.